[Bug tree-optimization/66558] New: Missed vectorization of loop with control flow

["alalaw01 at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66558

            Bug ID: 66558
           Summary: Missed vectorization of loop with control flow
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: alalaw01 at gcc dot gnu.org
  Target Milestone: ---
            Target: x86_64

ICC manages to vectorize the following loop, variants of which appear in
several benchmarks:

#define N 256
int a[N];

int
find_last (int threshold)
{
   int last = -1;

   for (int i = 0; i < N; i++)
    if (a[i] > threshold)
      last = i;

   return last;
}